1. Field of Invention
The present invention relates generally to the field of power detection. More specifically, the present invention is related to the use of directional couplers for accurate power detection.
2. Discussion of Prior Art
Directional couplers are very commonly used RF/microwave devices. Many companies design, manufacture and market various types of directional couplers. The following references provide for a general teaching with regards to directional couplers:
The U.S. patent to Grunewald (U.S. Pat. No. 6,998,936) provides for a broadband microstrip directional coupler, wherein the directional coupler comprises two ports connected by a first line and two second ports connected by a second line. The lines in Grunewald extend through a coupling zone in which they are separated by a conductor area not connected to the lines.
The U.S. patent to Sawicki (U.S. Pat. No. 7,009,467) provides for a multilayer coupled-lines directional coupler of the quarter wavelength type that combines a high-efficiency with low manufacturing costs.
The U.S. patent to Pelz (U.S. Pat. No. 7,015,771) provides for a directional coupler that uses non-metallic slotted spacers at the edges of a pair of coupled lines, wherein the spatial relationship between the coupled lines is therefore adjustable and does not depend upon extremely tight manufacturing tolerances.
The non-patent literature to Wang et al. titled “A study of meandered microstrip coupler with high directivity” provides a meandered structure to improve the directivity of a microstrip direction coupler.
The non-patent literature to Kim et al. titled “A design of single and multi-section microstrip directional coupler with high directivity” outlines the use of the distributed capacitive compensation to decrease the phase difference of even and odd mode.
Prior art power detection techniques utilize a single directional coupler. Further, the primary area of focus of the prior art involves improvements to the directivity of the directional coupler to minimize the uncertainty in power detection. A common problem with the implementation of such prior art techniques is that they result in a structure that is complicated and large in size. Therefore, with prior art practices, it is very difficult to realize a miniature directional coupler with decent directivity which can be integrated into the MMIC circuit or module.
Whatever the precise merits, features, and advantages of the above cited references/prior art techniques, none of them achieves or fulfills the purposes of the present invention.